Metacognitive knowledge is the concern of this paper; specifically children's knowledge of factors, such as their ability and effort, which affect their performance and their awareness of the integration of these factors. How a young child's familarity with his or her own mind might facilitate reasoning competence with respect to aspects--such as ability and effort--of a mental task like reading words, is examined. Results showed that children do seem able to reason in a relatively sophisticated way about the separate and combined effects of their mental ability and effort on their success and failure. They are able to discriminate attributions, consider the negation and reciprocal relationships among the attributes separately, and integrate them. (Author/GK)